Device For The Detection Of Non-Cavitated Early Dental Caries Lesions

ABSTRACT

The invention provides a device for detecting non-cavitated caries lesions, including a measuring electrode having an electrically conductive tip. The tip is dimensionally configured to fit within a fissure and provide electrical contact with a patient&#39;s tooth. A reference electrode is also included, the reference electrode being configured for electrical contact with the patient&#39;s body. A measuring means is also provided for determining electrical conductance between the measuring electrode and the reference electrode, wherein the device is further configured to receive a current source for providing electrical current between the measuring electrode and the reference electrode.

FIELD OF THE INVENTION

The present invention relates generally to detection of dental carieslesions. More particularly, the present invention relates to electricaldevices and methods for detecting non-cavitated early dental carieslesions.

BACKGROUND OF THE INVENTION

Dental caries is a disease that frequently occurs soon after teeth eruptinto the oral cavity, an environment that is generally hostile to theteeth of most individuals. Sites particularly prone to cariesdevelopment are the occlusal surfaces of the posterior teeth. This islargely because these surfaces possess a morphology (i.e. pits, fissuresand fossae) that favors retention of both fermentable carbohydrate andbacterial biofilms. These two entities are primary elements in dentalcaries causation. Combined, they result in the production of the acidthat leads to tooth demineralization and the initiation and developmentof dental caries lesions. More tooth decay occurs in occlusal locationsand to lesser degree in interproximal dentition sites (where teeth arein contact with one another) than elsewhere in the human dentition. Thisis because bacteria and fermentable carbohydrate collect more easilythere, and are protected from the caries inhibiting effects of saliva,than occurs in other more salivary accessible dentition locations.

Dental caries begins as a demineralization process which leads to thedevelopment of pores and tunnels through the protective,non-electrically conductive enamel (Longbottom, C. and Huysmans, M. C.D. N. J. M. Electric measurements for use in caries clinical trials.Caries Res. 29, 94-99, 1995. Longbottom C and Huysmans M. C. D. N. J. M.Electrical measurements for use in caries clinical trials. J. Dent. Res.83 (Spec. Issue C) C76-C79, 2004). Continued demineralization eventuallyresults in enamel breaching. Once the enamel is breached, cariesadvances and spreads rapidly through the underlying dentine, a tissuemuch less mineralized than enamel. Such spreading is made easy becausedentine is traversed by numerous tubules. Many, if not most of thesedentinal tubules, especially in younger teeth, reach all the way to thedental pulp (Pashley D. H. Theory of dentin sensitivity. J. Clin. Dent.5:65-67, 1994).

Non-cavitated caries lesions, particularly in the pits, fissures andfossae of the posterior teeth are difficult to detect and assess inhumans. Teeth mainly involved include the first and second primarymolars and the premolars and molars of the permanent dentition. Theseteeth and interproximal dentition sites are where the majority of dentalcavities occur.

Presently, detection of caries development is mostly done by a dentistor other dental care provider with a simple, pick-like device, generallyreferred to as a dental explorer. Such detection is performed by visualexamination for indications of mineral loss, and is done with or withoutx-rays. None of these tools is suitable for detection of a highpercentage of non-cavitated occlusal caries lesions even when there iscaries penetration into the dentine. Many of these early developingcaries lesions are not cavitated, but do involve extensive tunnelingthrough the enamel and such tunneling may not be detectable. Such cariesdevelopment is frequently hard to discover until destruction of toothsubstance becomes more substantial and the dentine becomes progressivelymore and more involved. As a consequence of the difficulty of theirdiscovery, these lesions are commonly referred to as hidden dentalcaries (Weerheijm K L, van Amerongen W E, and Eggink C O. The clinicaldiagnosis of occlusal caries: A problem. J. Dent. Child. 56, 196-200,1989). Their early discovery is often missed or involves muchuncertainty. Not surprisingly, there is opportunity for pulpal damage tooccur and for teeth to be lost unnecessarily (Verdonschot E. H., WenzelA., Truin G. J. and Konig K. G. Performance of electrical resistancemeasurements adjunct to visual inspection in the early diagnosis ofocclusal caries. J. Dent. 21: 332-337, 1993). Ironically, theanti-caries agent, fluoride, can be detrimental to early detection,because it favors less cavitation (Hudson P. and Kutsch V. K.Microdentistry: Current pit and fissure caries management. Compendium22: 469-483, 2001). This is because fluoride reduces the solubility ofthe enamel covering the dentine, thereby enabling the enamel to remainlargely intact while underlying dentine continues to be demineralized(Lussi A., Firestone A., Schoenberg V., Hotz P., and Stich H. In vivodiagnosis of fissure caries using a new electrical resistance monitor.Caries Res. 29: 81-87, 1995). For these reasons, it has become veryimportant that caries lesions be detected as early and as easily aspossible.

Because the enamel of freshly erupted teeth commonly exhibit a certaindegree of porosity, such teeth are more prone to dental cariesdevelopment than if they had been exposed in the mouth for an extendedperiod under non-cavity producing and mineralizing conditions. Suchimprovement is called maturation and occurs because many of theseexposed teeth acquire calcium and phosphate ions from saliva along withvarious proteinaceous accretions. These changes involve increased enamelmineralization, reduced enamel permeability and greater cariesresistance. This is helped by fluoride if applied or taken up naturallyduring the tooth maturation process (Ie Y. L., Verdonschot E. H.,Schaeken, M. J. M. and vant Hof M. A. Electrical conductance of fissureenamel in recently erupted molar teeth as related to caries status.Caries Res. 29: 94-99, 1995). In contrast, in a caries-prone mouth wherea demineralization environment is present, an opposite result occursmore readily, i.e. development of increased porosity and cavitation.

Several approaches have been unsuccessfully used to detect dental cariesin its early stages. One of these involves testing for a tooth's abilityto conduct electrical current even when there is no visible toothmineral loss from the enamel and no cavitation can be seen. Electricalresistance is associated with the presence of intact, non-demineralizedenamel; but, as a caries lesion develops and enamel mineral isprogressively lost, fluid can seep therein and electrical resistance ofthe enamel correspondingly and progressively decreases (Williams, D. L.,Tsamtsouris A., and White, G. E. Electrical resistance correlation withtactile examination on occlusal surfaces. J. Dent. Res. 57: 31-35, 1978,Longbottom C and Huysmans M. C. D. N. J. M. Electrical measurements foruse in caries clinical trials. J. Dent. Res. 83 (Spec. Issue C) C76-C79,2004).

Breaching of enamel occurs more easily in occlusal pit and fissuresites. As noted above, these dentition locations are where continualpresence of acidogenic bacteria and fermentable carbohydrate can undergosignificant and continual interaction. This favors prolonged generationof acid and in turn, prolonged and extensive tooth demineralization. Asthis happens, a point is reached where the enamel is sufficientlydemineralized and porous that saliva penetrates therethrough and becauseof the ions that saliva contains, flow of electrical current can takeplace as a result. The more extensive the demineralization, the morereadily these events occur and the easier it is to detect caries lesiondevelopment.

Earlier investigators measured electrical resistance or conductivitywith direct current devices to determine if a tooth had lost mineral andhad become carious (Pincus, P. A new method of examination of molartooth grooves for the presence of dental caries. J. Physiol 113: 13-14,1951. Mumford, J. M. Relationship between the electrical resistance ofhuman teeth and the presence and extent of dental caries. Brit. Dent. J.100, 239-244, 1956. Mayuzumi, Y, Suzuki, K and Sunada, J. A method ofdiagnosing incipient caries in pits and fissures by measuring electricalresistance. J. Dent. Res. 43, 431, 1964. Takeuchi, M., Kizu, T., S{acuteover (h)}imizu, T., Eto, M. and Amano, F. Sealing of the pit and fissurewith resin adhesive. II. Results of nine months' field work, aninvestigation of electrical conductivity of teeth. Bull Tokyo Dent Coll7, 60-71, 1966. Williams, D. L., Tsamtsouris A., and White, G. E.Electrical resistance correlation with tactile examination on occlusalsurfaces. J. Dent. Res. 57: 31-35, 1978). Others subsequently usedalternating current and measured impedance to do essentially the samething (White G. E., Tsamtsouris A., and Williams D. L. A longitudinalstudy of electronic detection of occlusal caries. J. Pedod. 5, 191-201,1981. Pitts N. B. Clinical diagnosis of dental caries: a Europeanperspective J. Dent. Educ. 65: 972-978, 2001). In each case, a cavitydetecting device was provided, including a measuring probe made of aconducting metal, a direct or alternating current source, a resistancesource, an impedance or conductance detector, and a reference electrodesuitable for application, generally by attachment to a non-oral softtissue part of the body. The human body is sufficiently conductiveelectrically to enable complete electrical continuity via the bodybetween the measuring probe (i.e. the indicator electrode) and areference electrode usually attached by adhesive means to a body surfacesuch as the ventral surface of the forearm or the back of the neck or bymeans of a metal hook, the end of which is immersed in the mouth salivausually by curling around the lower lip.

Tooth enamel is electrically non-conductive unless it is breached bydemineralization or fracture. When this occurs, fluid at or entering thebreached enamel site enables completion of an electrical circuit thatallows current to flow. The electrical current used may be as low as afew micro-amperes (μA) in magnitude. Hence, it is safe even for use inmedically compromised patients. In addition, the procedure is painless.

It has previously been found that special precautions have to be takenwhile making measurements to ensure electrical continuity withoutcausing any peripheral electrical conductance to saliva or othermoisture on the tooth or to saliva or other conductance means elsewherein the mouth. Such isolation of the measuring electrode from surroundingsaliva is an absolute requirement for success. Complete isolation can beachieved by using a rubber dam (Williams, D. L., Tsamtsouris A., andWhite, G. E. Electrical resistance correlation with tactile examinationon occlusal surfaces. J. Dent. Res. 57: 31-35, 1978). However, such useof a dam is cumbersome and is not practical when an extensive mouthexamination is required. Instead, most investigators have used a streamof air from an air syringe in an attempt to dry the tooth around but notat the measuring site. To do this simply, consistently and rapidly hasbeen a major problem.

Ricketts et al. used a stream of air surrounding the measuring electrodeto isolate the measuring site from surrounding surface electricalconduction (Ricketts, D. N. J. Kidd, E. A. M., and Wilson, R. F. Are-evaluation of electrical resistance measurements for the diagnosis ofocclusal caries. Brit. Dent. J. 178: 11-17, 1995). However, the largesize of the measuring tips used by these investigators preventedaccurate measurements. Further, such large tips, with their dryingfeature, were not suitably shaped or sized for many of the sites thatrequired more effective probing.

Current methods often yield false and/or variable readings. Currentmethods also lack the ability to rapidly and consistently detectnon-cavitated caries lesions early and accurately. Basically, detectionof non-cavitated caries lesions requires electrical linkage between themeasuring electrode at the enamel surface measuring site and fluidwithin the caries lesion. Detection also requires the absence of anyelectrical conductance immediately around the lesion site. Furthermore,a method of instantly knowing that detection is operating properly isnecessary.

SUMMARY OF THE INVENTION

The invention provides a device for detecting non-cavitated carieslesions, including a measuring electrode having an electricallyconductive tip. The tip is dimensionally configured to fit within afissure and provide electrical contact with a patient's tooth withoutthe addition of an external electrical conducting means betweenmeasuring tip and tooth. Various fluids have been used in the prior artfor this purpose. A reference electrode is also included, the referenceelectrode being configured for electrical contact with the patient'sbody. A measuring means is also provided for determining electricalconductance between the measuring electrode and the reference electrode,wherein the device is further configured to receive a current source forproviding electrical current between the measuring electrode and thereference electrode.

The invention also provides a method for detecting non-cavitated carieslesions. The method includes the steps of providing a referenceelectrode for electrically conductive contact with a patient's body, andproviding a measuring electrode having an electrically conductive tip,which is dimensionally configured to fit within a fissure and provideelectrical contact with a patient's tooth without the addition ofelectrical conducting means between measuring tip and tooth. Themeasuring electrode is configured to fit within a fissure and provideelectrical contact with a patient's tooth. Electrical current isprovided between the measuring electrode and the reference electrode,and electrical conductance between the measuring electrode and thereference electrode is determined.

These and other objectives and advantages of the present invention willbe more readily apparent from the following detailed description of thedrawings and preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

FIG. 1A is a schematic representation of a probe being introduced into afissure, according to the present invention;

FIG. 1B is a schematic representation of a fissure having a narrow slit;

FIG. 1C is a schematic representation of a fissure having the shape of aconstricted hourglass;

FIG. 1D is a schematic representation of a fissure having an invertedY-shaped division;

FIG. 2A is a schematic representation of a fissure in enamel beforedrying;

FIG. 2B is a schematic representation of a fissure in enamel afterdrying;

FIG. 2C is a schematic representation of detection via a prior artelectrode probe after drying;

FIG. 2D is a schematic representation of detection via an electrodeprobe according to the present invention;

FIG. 3A is a schematic perspective view of a hand-held measuring probe,according to the present invention;

FIG. 3B is a schematic perspective view of a removable measuring tipmounted to the probe of FIG. 3A.

FIG. 4A is a schematic representation of a measuring tip, according tothe present invention;

FIG. 4B is a schematic side view of a measuring tip, according to thepresent invention;

FIG. 5 is a schematic representation of the components of an embodimentof the present invention;

FIG. 6 is a schematic front view of the front panel of an embodiment ofthe present invention;

FIG. 7 is a graph showing the relationship between electricalconductance and demineralization;

FIG. 8 is a graph showing the relationship between electricalconductance and probe tips of different tip diameters in a molar toothfissure site;

FIG. 9 is a graph showing the relationship between electricalconductance and commercially available explorer tip diameters in a molartooth fissure site; and

FIG. 10 is a graph showing the relationship between electricalconductance and the diameter of different commercially available dentalexplorers in another (less accessible than in FIG. 10) molar toothfissure site.

FIG. 11 is a graph comparing detection of carious and sound toothsurfaces at baseline and after 14 months by visual-tactile (VT) andelectrical conductance (EC) means as per Tables 6 and 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1A is a schematic representation of a probe being introduced into afissure 120. As used herein, the term “fissure” may include any toothpits, fissures, fossae, or other similar regions or irregularities inthe tooth. As indicated in FIG. 1A, early dentinal caries lesions 140may form and spread out below the enamel 110. These early dentinalcaries lesions 140 are very common and are usually incapable of beingdetected through a traditional visual-tactile inspection or by x-rays.Conventional measuring probes 130 are either too large or not properlytapered to reach sufficiently into the pits and fissures where theselesions are mostly found, as will be described below in more detail (seeFIGS. 2C and 2D). The size and shape of the measuring electrode tip 130is crucial to early caries lesion detection 140 and in the obtaining ofconsistent and accurate measurements.

As seen in FIG. 1A, the fissure 120 formed in the enamel 110 may beginas a wide opening at the top of the enamel and become narrower towardsthe dentin. It will be understood that fissures 120 may also be formedin the enamel 110 in various shapes. For example, fissures 120 may bewide at the top and gradually narrowing toward the bottom as seen inFIG. 1A. The fissures 120 may also have almost the same width from topto bottom or include extremely narrow slits as seen in FIG. 1B. Fissures120 may also include inverted Y-shaped divisions (FIG. 10) or be formedas constricted hourglasses (FIG. 1D). In some embodiments, the width ofthe fissure 120 ranges from about 0.05 to about 0.3 mm. In at least someembodiments, the width of the fissure 120 ranges from about 0.1 to about0.2 mm. The length of the fissure 120 may be from about 0.5 mm to about1.5 mm. The length of the fissure 120 may also be from about 0.75 mm toabout 1.25 mm.

Thus, an important distinction between the present invention and theprior art is the difference in size and shape of the measuring electrodetip 130. Thus, the present measuring probe 130 is smaller in diameterand more appropriately tapered so that it can reach more deeply intopits and fissures (and other poorly accessible sites). The dimensions ofthe probe tip 130 enable contact with fluid present more deeply withinthe enamel and dentin beneath the enamel (or cementum) at breachedsites. Such fluid is almost always present but not in sufficientquantities and close enough to the enamel surface after drying to bereached consistently with the electrodes used in the prior art formaking accurate electrical conductance or resistance measurements, andparticularly without the need for an external electrical conductingmeans between measuring tip and tooth.

Turning to FIGS. 2A-2D, if there is electrical continuity between thetip of the measuring electrode and fluid 220 within an early enamellesion, then there is no need to apply a conducting fluid or mediumbetween electrode and lesion as has been required in the methods putforth in the prior art. However, if the probe tip does not reach fluid220 after drying the tooth surface with blown air, then the result is anopen circuit. Probes 250 that do not penetrate sufficiently, easilyresult in some air remaining between probe tip 250 and fluid 220 withinthe lesion as seen in FIG. 2C. This does not happen when probe tips 260are smaller, and more appropriately shaped and positioned as in FIG. 2D.This is because air is non-conducting and if sufficient air is leftafter air drying, then there will be no current flow. The result is azero electrical conductance reading (i.e. a false negative), which isalso the reading obtained when there is no caries lesion present (i.e. atrue negative). Inadequate surface drying can be a significant problem,because excess surface moisture will yield a reading suggesting lesionpresence (i.e. a false positive) when such is not the case.

As noted above, use of a rubber dam to isolate a tooth from itsgenerally wet, oral surroundings will make achievement of the necessarydrying conditions certain. By this means, there is no saliva at themeasurement site contiguous with saliva or other conducting fluid in themouth. With rubber dam use, one has complete tooth isolation and canfreely employ a conductive means, such as saline or a paste such astoothpaste. These will readily ensure electrical continuity betweenmeasuring probe and fluid within the caries lesion (Williams et al,1978). However, in the absence of a rubber dam a conductive means suchas toothpaste may have constituents that cannot be dried and collateralconductance cannot be avoided. However, as pointed out above, use of arubber dam as a saliva barrier device results in a very slow examinationprocess and hence is not clinically practical, except perhaps in limitedcaries diagnostic situations.

Previous investigators have dipped the measuring end of the measuringprobe into a patient's saliva, or another conducting fluid, paste, orsalt solution such as saline just before probe placement followed by airdrying (Williams et al, 1978). This has proven difficult to do rapidlyand consistently while ensuring probe and caries lesion electricalconnection without lateral saliva conductance. From such attempts, itbecame clear that drying to avoid lateral oral electrical conductancewas too difficult to achieve consistently, repetitively and within ashort period of time such as a few seconds. It is important to be ableto probe each tooth within such a time period in vivo. Otherwise, theprocedure (especially if multiple tooth examination is desired) can taketoo long and becomes impractical.

Lussi et al (1995) like Ricketts et al (1995) above used a shield fordrying around the measuring site and measuring tip with some success,while others tried to achieve reproducibility simply by applying aconstant flow of air for a fixed period of time. However, the formerreduces probe access capability and rapid probing to identify sites ofconductance. The latter standardized drying procedure has proven to beless suitable and reliable for clinical investigation or clinicalpractice than is desirable.

In contrast to conventional measuring electrodes, the present inventionutilizes electrodes with a shape and dimensions that enable suitableplacement and penetration of the measuring probe into pit and fissuresites as seen in FIG. 2D. This method enables the measuring electrode260 to be placed into a pit or fissure wherein (i) deep lying dentinalfluid is difficult or impossible to displace during air drying and (ii)coronal seepage of pulpal/dentinal fluid (because of hydrostatic andcapillary pressures that exist within dentinal tubules; Brannström,1967), was sufficient to ensure access by a more effective penetratingelectrode, even after significant drying of the tooth surface around themeasuring site. When breaching occurs, dentinal tubules are exposed andtubules become open to the oral environment. As a consequence, coronalmeasurement of dentinal fluid conductance, both electrical andhydraulic, can be more readily accomplished (Brannström, et al, 1966 and1967). Air drying may reduce superficial fluid within a breached site,but coronal seepage from the depths of breached sites can spontaneouslymake up for such fluid deficiency.

As a protective layer, root cementum behaves like enamel but itsbreaching differs from enamel in that cementum is thinner and generallymore porous and very hard to keep dry.

FIG. 3A is a schematic perspective view of a hand-held measuring probe300. Specifically, a hand-held measuring probe 300 consists of threeparts, an electrically insulated handle portion 330, an insulatingtightening knurl 320 and an easily replaceable, removable, substantiallyright angle shaped, measuring probe attachment or probe tip 310 (seeFIGS. 3A and 4). The probe tip 310 may be made from a metal such asstainless steel, which is very strong, flexible, and able to withstandthe physical manipulation and stresses involved. The measuring probeattachment 310 is preferably right angle shaped to make it easier toline up the probe tip for direct insertion into a tooth site ofinterest. Other angulations are also possible but are less desirable.The part of the removable measuring tip 310 that is inserted into thetightening knurl 320 may range from 20.0 to 40.0 mm in length. In someembodiments, the part of the removable measuring tip 310 that isinserted into the tightening knurl 320 and/or handle 330 isapproximately 30 mm in length. Furthermore, this portion may range from1.0 to 2.0 mm in diameter. In some embodiments, the portion is 1.5 mm indiameter. The distance from the bend to the tip may range from 6.0 to9.0 mm. In some embodiments, the distance is 7.5 mm. The diameter afterthe bend before tapering to a sharply pointed cone may be in the rangeof 0.2 to 0.4 mm. In some embodiments, the diameter after the bend is0.3 mm. As seen in FIG. 4A, the tip needs to include a taper to achievea sharp point. In a suitable embodiment, the taper to the sharp pointfalls in the range between 5° and 30°. A taper to a sharp point at anangle of 10° is preferable. This results in the length of the taperbeing 1.8 mm as illustrated in FIG. 4B. In some embodiments, the lengthof the taper may be between 1.6 and 2.0 mm. The shape and sharp tipenables maximum penetration of the measuring probe into pit and fissuresites to where it is easier to have fluid consistently present asdescribed in FIG. 2. In some embodiments, the tip has a diameter of 0.04to 0.06 mm with a preference of 0.03 to 0.05 mm.

An easily attached and removable tip that is disposable is highlydesirable for ease of use and to ensure no contamination. The probe partmay be made from a metal of sufficient strength and flexibility toenable shaping to a fine measuring tip and to be capable of of re-use ifdesired. Orthodontic stainless steel wire that has proven suitable forthis purpose has been identified as 304V (Rocky Mountain Orthodontics,Denver, Colorado). It has the chemical formula: Carbon 0.066%, Manganese1.26%, Phosphorus 0.018%, Sulfur 0.001%, Chromium 18.59%, Nickel 8.80%,Molybdenum 0.15%, Nitrogen 0.025%, Copper 0.25%,Cobalt 0.15%, with Ironmaking up the balance. This wire material and its probe tips are easy tosterilize with minimal effect on their physical and electricalproperties. For commercial reasons, because the probe electrodes aresimple and can be made inexpensively, they may be made disposable. Ifso, attachment to the handle of the measuring electrode can be by aknurl means or by spring tension contact between extension and coilingof the rigid part of the electrode tip 310 which is inserted into thehandle 320, where it makes electrical contact.

Referring to FIG. 3B, a removable electrode tip 325 is shown mounted onprobe 300. Tip 325 includes a tapered tip housing 322 with an opening324 at the distal end and a snap fit or threaded portion at the proximalend 326. Electrode tip 310, having a co-axial stiffening sheath 340passes through opening 324 of housing 322 and is secured therein, andterminates in coiled spring section 350.

Probe 300 terminates in an electrode end having a tip anchor 342 with anelectrical contact 344 protruding therethrough. In operation, tip 325 ismounted to probe 300 by securing the snap-fit or threaded portion of tiphousing 322 to anchor 342. At the same time, coiled spring section 350is compressed onto and brought into electrical contact with electricalcontact 344.

Use of an indicator electrode with the penetrating electrode tip justdescribed, eliminates the need for a fluid applied orally as aconducting means. In prior approaches to measuring conductivity, theelectrode dimensions and shape required application of a fluid to ensureelectrical contact with dentinal fluid. The present approach simplifiesthe invention considerably by eliminating this requirement and mostimportantly, it enables the user of the device to make measurements muchmore rapidly and accurately than previously possible.

Drying of any saliva on the tooth surface to eliminate surfaceelectrical conductance is usually accomplished with a brief 5 to 10second blast of dry air from a dental air syringe. This easily driesmost occlusal surfaces and the entrances to pits and fissures undermeasurement but it has little or no effect on the fluid sitting moredeeply (and not readily reachable by the blown air) within the pit orfissure lesions being measured. Coating the measuring electrode with aconducting fluid such as saline by dipping the tip into such a fluid hasbeen used to facilitate conductivity with electrodes greater indimensions than those disclosed herein (Williams et al, 1978). But someair is commonly left in the process and a reading of zero results,whether there is a lesion present or not.

In essence, with conventional electrodes, accessibility is largelylimited to pit and fissure entrances as seen in FIG. 2C. Hence, an oralsource of electrical conducting fluid, whether it is saliva or anextra-oral occlusal additive, becomes necessary. This makes it hard toachieve reproducibility, especially in the short period of time neededin order for the process to be practical. In contrast, the presentinvention needs no conductance adjuvant.

Electrical Conductance Measurement

In order to detect caries lesions, electrical conductance may bemeasured. In some embodiments, a measuring instrument features: (i) abattery powered DC current source that supplies current as needed, (ii)a digital μA meter to measure current, (iii) a digital voltmeter tomeasure voltage (if desired), (iv) a circuit board that enables severalfunctions that facilitate the taking of rapid, stable and reproducibleconductance readings, (v) a reference electrode placed distant from themeasuring site so that it does not interfere physically withmeasurements at dentition sites of interest and (vi) an electricallyinsulated measuring indicator probe, with a handpiece (e.g. #XHP1,Ellman International, Oceanside, N.Y. 11572) and a replaceable measuringtip.

The 9 volt battery that powers the circuitry of the instant device mayproduce an unregulated current source limited to an output of 10 μA. Itprovides an open circuit output of 9 volts and 0 μA. These valuescorrespond to the situation where the probe is not in contact with atooth site under measurement or is in contact with a tooth site undermeasurement when the enamel is intact (i.e. with no demineralization).In contrast, if the enamel (or cementum) is breached, as occurs whensufficient caries demineralization has developed and the breach isfilled with dentinal or oral fluid, electrical conductance occurs. Whenthe electrical circuit is closed, the current rises to a value greaterthan zero. This occurs when there is a lesion and the rise in current isproportional to the magnitude of the lesion. Decrease in potential andresistance also occurs, as can be seen from Tables 1 and 2 below. Insome embodiments, no external electrical current is applied in order toensure patient safety.

TABLE 1 Table relating the Ohm's Law variables: conductance (I) toresistance (R), and electrical potential (V) when the battery voltage is8.61 volts. R (OHMS) V (VOLTS) I (MICRO AMPS) R = V/I Open 8.61 0.00 0.022.0M 8.30 0.37 22.0M 15.0M 8.27 0.55 15.0M 10.0M 8.24 0.81 10.1M 6.8M8.21 1.19 6.9M 4.7M 8.15 1.70 4.8M 2.7M 8.04 2.87 2.8M 1.8M 7.95 4.161.9M 1.0M 7.65 6.92 1.1M 800.0K 7.55 8.30 909.0K 600.0K 6.61 9.35 706.0K400.0K 4.82 9.54 505.0K 200.0K 2.93 9.72 301.0K 100.0K 1.98 9.82 201.0K80.0K 1.79 9.84 181.0K 60.0K 1.59 9.86 161.0K 40.0K 1.40 9.88 141.0K20.0K 1.20 9.91 121.0K 10.0K 1.10 9.92 110.0K 8.0K 1.08 9.92 108.0K 6.0K1.06 9.92 106.0K 4.0K 1.04 9.92 104.0K 2.0K 1.02 9.92 102.0K 1.0K 1.019.92 101.0K 0.0K 1.00 9.92 100.0KMeasurements showing that, as the electrical conductance increases, thevoltage and the resistance both decrease. This pattern is reflective ofincrease in severity of dental caries. The calculated values of circuitresistance closely match the resistance (R) column, R₁+Rs (100,000+1000Ohms).

TABLE 2 Table relating the Ohm's Law variables: conductance (I) toresistance (R) and electrical potential (V) when the battery voltage is6.37 volts. R (OHMS) V (VOLTS) I (MICRO AMPS) R = V/I Open 6.37 0.00 0.022.0M 6.34 0.28 22.6M 15.0M 6.33 0.42 15.0M 10.0M 6.30 0.63 10.0M 6.8M6.28 0.91 6.9M 4.7M 6.24 1.30 4.8M 2.7M 6.15 2.19 2.8M 1.8M 6.06 3.181.9M 1.0M 5.89 5.31 1.1M 800.0K 5.78 6.37 907.0K 600.0K 5.62 7.95 706.0K400.0K 4.82 9.54 505.0K 200.0K 2.93 9.73 301.0K 100.0K 1.98 9.83 201.0K80.0K 1.79 9.84 181.0K 60.0K 1.59 9.86 161.0K 40.0K 1.40 9.87 141.0K20.0K 1.20 9.90 121.0K 10.0K 1.10 9.90 111.0K 8.0K 1.08 9.91 108.0K 6.0K1.07 9.92 107.0K 4.0K 1.05 9.93 105.0K 2.0K 1.03 9.93 103.0K 1.0K 1.029.93 102.0K 0.0K 1.00 9.93 100.0KMeasurements showing that when the electrical conductance increases, thevoltage and the resistance both decrease. This pattern is reflective ofincrease in severity of dental caries. The calculated values of circuitresistance closely matches the resistance (R) column, R₁+Rs(100,000+1000 Ohms).Moreover, completion of the circuit when any reading is made may belinked to a maximum current flow of 10 μA. As seen in Table 3, mostearly lesion readings are below 4 μA:

TABLE 3 Electrical Conductance and Demineralization Scores of Test TeethCurrent Demineralization Tooth # (μA) score 32 1.9 2 15 3.0 4 2 3.0 4 152.0 3 2 3.0 4 2 3.0 3 1 3.0 3 32 2.0 2 19 1.0 1 1 2.0 2 16 0.3 0 19 1.02 15 2.0 2 30 3.0 3 18 3.0 2 19 3.0 3 19 1.0 1 31 3.0 4 15 13 1 32 0.8 11 1.3 1 16 1.7 1 30 0.9 1 1 1.5 1 31 2.7 2 19 1.9 2 Number 26 Mean =2.16 ± 0.55 Mean = 2.11 ± 0.67 of teeth

Circuit Description

In a similar examination of non-carious teeth (see Example 2 below),electrical conductance readings showed a mean value of 0.0 μA and meandemineralization scores were zero.

As seen in FIG. 5, during caries probing, the present device isessentially an open circuit instrument. The circuit is closed when thereis fluid traversing the lesion site and the fluid makes contact with ameasuring electrode with or without a conducting aid such as a paste orsaliva. The circuit may include a pathway of current flow from apatient's forearm, back of neck or cheek through his or her body to thepatient's tooth being measured. This circuit completion may be achievedvia the indicator and reference electrodes with a μA meter and/orvoltmeter measuring unit in between. A suitable reference is an EKG typeof silver/silver chloride electrode (Silver Mae Trade plus Tab,Cardiology Shop, Berlin, Mass. 0150) attached to the ventral surface ofthe forearm. A lip hook can also be used but is not desirable because ithinders application of the measuring electrode by the dentist or otherhealthcare worker.

As can be appreciated from FIG. 5, the present device may be powered bytwo batteries. The first battery powers a μA meter and if included, avoltmeter. The current source output voltage is unregulated (9 voltsdown to 1 volt) and the current output as indicated above is limited to10 μA. A second battery may power the current source circuitry and thecontrol and monitoring circuits (see above). This battery may have avoltage in the range 6.3 to 9.0 volts. At a voltage below 6.3 volts, thebattery should be replaced. In some embodiments, determination ofbattery life may include turning on a battery test switch. The firstbattery may be similarly replaced when the meter displays a low batterycondition.

A small load indicates the presence of a cavity at an early stage ofdevelopment; it is associated with a high resistance (e.g. 22 megohms).The lesion being evaluated in such a situation will draw a small amountof current and show a small decrease in the voltage. Should the load behigher, (e.g. one reflected by a resistance between 100,000 and 600,000ohms), the current flow will be greater; decrease in voltage will becomelarger and a more advanced cavity is indicated. Should the load be stillhigher, resistance will be very low (e.g. between 1,000 and 100,000ohms). The current will rise and reach close to the maximum current of10 μA; correspondingly, the voltage will drop to 1 volt and a moreadvanced cavity would be indicated.

Additional components in the completed meter circuit may include aresistor (R1), a resistance shunt (Rs) and the μA meter. R1 iscalculated by the formula R1=V/A where V is voltage and A is current inamperes. Design is such that the current source output voltage will dropno lower than 1 volt. This occurs when the reference electrode and thedental probe are intentionally shorted (no patient in the circuit) as isdone as a systems test, when carrying out pre-testing as describedbelow. The maximum current source output in this situation is 10 μA andR1=1 volt/10 microamps=100,000 ohms (see Tables 1 and 2).

The Rs shunt may be set to 1,000 ohms for a 200 μA digital panel meterwith a 200 my range (full scale). In that case, Rs=Vm/Im=200 mv/200μA=1,000 ohms.

The completed circuit meter readings in the instant device for variousresistance values placed between the reference electrode and the instantdevice probe, simulates dental caries conditions and the results areshown in Tables 1 and 2. The calculated resistance values will includethe circuit resistors, R1+Rs, as stated above; these values are shown inthe R=V/I column in Tables 1 and 2.

The voltage and current measurements with the present device (Tables 1and 2) both show a pattern that is directly related to dental cariespresence. The magnitude of the cavity is related to the magnitude of thecurrent, the voltage decrease and the combination of both the voltageand current changes. The battery voltage range differences are in Table1 (8.61V) and Table 2 (6.37V); they yield an insignificant difference incircuit resistance plus a micro-ampere difference ranging from 0 at 80Kohms to a maximum of 1.61 μA at 1 megohm.

The values for R=V/I, calculated using Ohm's Law, are shown in Tables 1and 2. The calculated values for circuit resistance closely match theOhms column and the R=V/I calculated resistance column; this includes R₁(100K)+Rs (1K) for both battery voltage levels.

Voltage Regulation

The present device may use a 9 volt unregulated, 10 μA current limitedpower supply. The use of an unregulated supply allows the voltage todrop (e.g. 9 volts to 1 volt) as the load is increased. If desired, thisallows voltage data to be recorded in addition to current data.

A constant voltage regulated supply limited to 10 μA output may also beused. The difference is that, as the load is increased, the voltageholds constant at 9 volts and the current still rises (e.g. 0 to 10 μA).The current data available are recordable and values are directlyrelated to the magnitude of the caries lesions.

In essence, the important aspect of the instant device is thedevelopment of (i) a specialized measuring probe, (ii) a method ofmeasuring electrical conductance that includes use of the conductivityof a patient's body and the supplying of a current source limited to 10μA of current and (iii) a method of being able to rapidly probe foractive sites and record conductance rapidly and accurately. As indicatedabove, measurement is one that either involves no conduction (i.e. opencircuit) when there is no caries, or one that does involve conduction(i.e. closed circuit) when there is caries present.

Processor and Storage

In some embodiments, the probe is coupled to a processor and a storagemedium. Any suitable processor can be used, including a combination ofindividual processors. Any suitable storage medium can be used. Storagemedia may include volatile, nonvolatile, removable, and non-removablemedia implemented in any method or technology for storage ofinformation, such as computer readable instructions, data structures,program modules, or other data. Examples of storage media include RAM,ROM, EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can be accessed by a computing device or other processor.Methods of communication between components of the arrangementsdescribed herein can include both wired and wireless (e.g. acousticradio-frequency, optical, or infrared) communications methods. By way ofexample, wired communications can use items such as twisted pair,coaxial cable, fiber optics, wave guides, and other wired media andwireless communications can use methods such as those above.

In at least some embodiments, the processor is coupled to a storagemedium and sends data to the storage medium for storage or furthercalculations. In some embodiments, the storage medium may be portable,such as a compact disk. The storage medium may automatically record orlog data sent to it by the processor. In some embodiments, the storagemedium stores patient data in a log including, for example, patientname, date of visit, number of caries detected and/or location ofcaries.

The processor may also be coupled to an indicator. The indicator may beconfigured on either a probe or as part of the processor. In at leastsome embodiments, when a caries lesion is detected, one or more signalsmay be emitted. In another embodiment, a signal may be emitted whenelectrical conductivity is first detected. Many different types ofsignals may be emitted from the indicator including, for example, atleast one auditory signal, at least one visual signal, at least onetactile signal, at least one olfactory signal, a telemetry signal toanother device, or the like or combinations thereof. For example, anemitted signal may include one or more beeps, chirps, squeaks, chimes,rings, the activation or de-activation of one or more lights orlight-emitting diodes one or more times, a message may be displayed onone or more displays, one or more vibrations or tactile pulses, theemission of one or more peculiar odors, and the like or combinationsthereof. The indicator may be activated for any set period of time. Insome embodiments, the indicator is activated for at least a period of 3to 5 seconds, so that the dentist or dental care provider such as ahygienist can verify or record the presence of the caries.

As discussed, the processor may be coupled to an indicator in the formof a message or emitted signal. Alternatively, the indicator may be inthe form of a graphical representation of the teeth. As the probe ismoved over the teeth, the area may be mapped onto a graphicalrepresentation, showing possible caries. Such a graphical representationmay be helpful in identifying possible problematic areas for theattending dentist or dental care provider.

Device Operation.

FIG. 6 is a schematic front view of the front end of a caries measuringinstrument. Operation of the device may be as follows: (i) Theinstrument is turned on by moving switch S1 to the ON position; the μAmeter will read 0.00. If a low battery condition is displayed, the meterbattery needs to be replaced; (ii) Switch S2 is moved to the BATTERYTEST position; the current source battery needs to be replaced if thetest light does not illuminate; (iii) Switch S2 is moved to the ONposition and (iv) the probe and reference electrode, which are connectedto the device by jacks, are used to test whether the circuits arefunctioning properly. The output of the current source supplies 9 voltsat 0 μA in the open circuit state and a maximum of 1 volt and 10 μA inthe shorted closed circuit condition, i.e. when reference and probeelectrodes are in contact with each other.

To carry out the testing, readings may be made by first having thesystem in its open position and to then test if reading range is at itsmaximum. For the latter, the probe tip is placed in contact with thereference electrode so that the circuit is shorted. This activates anauditory component (a beeper) in the measuring unit for a period of timethat indicates to the operator that he or she has made electricalcontact. In some embodiments, the auditory component is activated for 1,2, 3, 4, 5 or 10 seconds. When the beeping of the auditory componentstops, the electrode is removed from contact with the measuring site. Atthe end of the beep, a five second numerical hold circuit is triggeredwhich results in the display of no more than 10 μA on the μA meter andno less than 1 volt on the voltmeter. The reading may hold for fiveseconds to allow time for reading recording; the meters then return tozero μA and full battery voltage. The system is now ready for successiveintermittent probing for hidden dental caries lesions with the indicatorelectrode. Sliding probing can also be done where the probe is run alongfissures and a beep or beeping will locate early hidden caries lesions.An immediate intermittent probe thereafter will confirm lesion presenceand its magnitude.

To enable device portability, batteries may be used. This eliminates theneed for patient isolation techniques, power cords and reduces cost. Aline powered or battery eliminator can also be constructed. The use ofline power or a battery eliminator transformer requires a power cord andthe addition of patient isolation techniques. The voltages supplied toand by the circuitry in the meter are set and will not vary like abattery can, as it gradually discharges during use. Circuit operation ofthe current source is the same.

These features will allow the same data from all such meters. Ifeliminating the need to manually record data is desired, a method may beintroduced to record the data in a memory or print the data instead.

The details of the device are provided in the Examples given below whichare provided as an illustration of the invention only and thereforeshould not be construed to limit the scope of the present invention.

Example 1

An apparatus was assembled to simulate the in vivo condition to showthat fluid can move coronally through the apical foramen of a tooth(from underlying tissue fluid) and then through the pulp and thereafterthrough the dentine to fill any breached or partly breached (porous)enamel spaces. In doing so, the nature of the electrical conductancecircuit involved is demonstrated along with its open and closed natureduring measurements.

The apparatus is also of considerable use for the testing beforehand ofprobe tips for their suitability for use in the measuring instrument. Itis also of use for training health care providers before proceeding towork on patients.

The device consists of a Petri dish (9 cm diameter) without its lid,covered with a rubber or cardboard sheet (15 cm square×2 mm thick) witha hole in the center for a tooth to be placed in an upright positionready for probing and electrical testing (cf. rubber dam used in vivo).Another hole in the sheet is used to accommodate a reference electrodeas above. Still another hole is cut to enable addition or removal ofsaliva, serum or other fluids, as desired or appropriate.

The sheet is supported by a 15 cm×7 mm thick wooden frame placed overthe Petri dish. Thirty ml of 0.9% (w/v) NaCl solution (i.e. saline) isadded to the Petri dish and the roots of each tooth undergoingmeasurement is pressed through the hole in the center of the rubbersheet until the apical portion of the root is immersed about 2 to 3 mminto the saline in the Petri dish. The saline enters the pulp chamberthrough the root canal or canals of the tooth being tested. It thenpasses from the pulp and through the dentinal tubules to reach the pits,fissures or fossae under test. If any covering enamel is not intact(i.e. porous or breached), then current will be detected and measured.

The reference electrode utilized in making conductance determinationsconsists of a convenient length of platinum wire placed into the salinesolution in the Petri dish and is connected to an insulated wire leadingto the measuring instrument. The indicator electrode and its replaceablemeasuring tips may be similar to those described above with reference toFIGS. 3 and 4.

Example 2

In a set of experiments to compare sound and carious teeth and confirmsuch to be the case by biopsy, electrical current at 6 to 8 occlusalsurface sites per tooth were measured in 26 non-cavitated carious and in13 freshly erupted (and hence, clearly non-cavitated and non-carious)teeth. At each site, readings were made in triplicate. Each timebeforehand, the tooth was dried by air-blowing for 5 to 10 seconds priorto the taking of measurements. The crown of each tooth was thensectioned transversely with tooth slices cut progressively from theocclusal to the cemento-enamel junction area. This gave slices that wereeach 630 μm thick. In a re-constructed sectioned tooth, slices would bespaced 150 μm apart due to the thickness of the diamond blade in a lowspeed saw (Isomet 11-1180, Buehlar, Evanston, Ill.) used for theslicing. Each horizontal section was photographed in color and examinedvisually for demineralization, which indicated extent of lesionprogression and was scored on a scale of 0-4.

Electrical conductance ranged between 0.3 and 3 μA in the occlusal sitesin the 26 carious teeth measured as seen in Table 3 and was zero in allof the occlusal sites measured in the 13 non-carious controls as seen inTable 4. The teeth identified in Tables 3 and 4 are numbered inaccordance with the Universal System of Tooth Numbering. The rightmaxillary third molar is designated “1” and the count increases to theleft. The left mandibular third molar is designated “17” and the countincreases to the right along the bottom teeth.

TABLE 4 Electrical current and Demineralization Scores of Control TeethCurrent Demineralization Tooth # (μA) score 1 0.0 0 15 0.0 0 32 0.0 0 320.0 0 32 0.0 0 17 0.0 0 16 0.0 0 19 0.0 0 16 0.0 0 3 0.0 0 32 0.0 0 160.0 0 31 0.0 0 Number 13 Mean = 0.0 Mean = 0 of teeth

Visual examination of the horizontal sections of the carious group ofteeth showed a mean demineralization score of 2.11±0.67 (S.D.) (seeTable 3 above) on a 0-4 scale as described below in Table 5. Their meanelectrical conductance value (see Table 3) was 2.16±0.55 (S.D.) μA. Incontrast, the control group of teeth showed a mean electricalconductance of 0.0 μA (Table 4) and no mineral loss was visible in thesesections. Their mean demineralization score was 0. The difference in theelectrical current values between the two groups was highly significantby the Student t test as was the difference in their demineralizationvalues (p<0.001).

Example 3

The occlusal surfaces of forty extracted permanent molars were eachfirst measured with the measuring device to detect presence of carieslesions and to then confirm their presence by tooth biopsy as in Example2 above. This group of teeth showed electrical current values between 0and 4 μA. Occlusal sites were selected in each slice and electricalconductance was measured in each location in triplicate. The teeth werethen biopsied by sectioning as in Example 2 and visually examined andscored for demineralization from color photographs thereof. Electricalcurrent was plotted against demineralization scores (FIG. 7).Correlation between electrical conductance and detection by biopsy wasvery high (r=0.914; p<0.001).

Example 4

Batteries lose voltage with use. Such discharge may affect the stabilityof instrument readings. To test for this possibility, a 100K resistorwas introduced into the instant device between the probes of themeasurement instrument. This adds to RI and Rs a value of 101,000 ohms.In Table 1, with a battery voltage of 8.61 volts, the instrument reads1.98 volts and 9.82 μA. Using Ohms Law, R=V/I, this works out to 201,000ohms. Table 2 shows similar measurements when the battery voltage is6.37 volts. Connecting the same 100K resistor between the probes of thepresent device results in meter readings of 1.98 volts and 9.83 μA. Thisalso calculates out to 201,000 ohms.

In comparing Tables 1 and 2, the differences in the calculated values ofcolumn R=V/I are insignificant. A review of the μA column shows adifference of 0 μA at 80,000 ohms, and a maximum difference of 1.6 μA at1,000,000 ohms. This difference in μA may be insignificant indetermining the magnitude of caries lesions. Thus, the accuracy of themeasuring device in detecting dental caries has been demonstrated. Thus,readings are not affected as the 9 volt battery power source loses someof its charge.

Example 5

A 14-month study was carried out to compare detection in vivo ofocclusal caries lesions in the occlusal surfaces of the first permanentmolars of Venezuelan children by electrical conductance and byvisual-tactile means. Two hundred children, 9 to 11 years of age, fromUnidad Educativa Baute in Venezuela participated in this investigation.Of the 200 children accepted, 119 remained at the end of thisinvestigation and these are the basis of the data analysis. Thevisual-tactile and electrical conductance methods were both used todetect carious lesions at baseline and after 14 months. The occlusalsurface examinations were done by two examiners. One performed thevisual-tactile examination using artificial light, probe and dentalmirror; the other utilized the caries detection device of the presentinvention. Both examiners were standardized beforehand for theirrespective methods. Visual-tactile examination used a DMFS scoringprocedure based on the criteria shown in Table 5:

TABLE 5 The recording criteria used in the visuo-tactile examinationmethod. 1a: Change in enamel surface translucency or 2: Filled toothsurface   opacity that is distinctly visible after air   drying 1b:Opacity distinctly visible while surface is 3: Extracted tooth   stillwet.  surface 1c: Localized enamel breakdown where 4: No or slightchange in   the enamel is opaque or discolored.  enamel translucency (sound) 1d: Cavitated enamel 5: Unerupted surface DMFS scoring: 1a, bor c is scored D ½; 1d is scored D1; 2 is scored Filled; 3 is scoredMissing; and 4 is scored Sound.For this example, surfaces were scored carious if any of criteria 1a to1d were met and sound if criterium 4 was met. The results of suchcarious/sound scoring are shown in Tables 6 and 7, below:

TABLE 6 Number and percentage of occlusal surfaces in first permanentmolar teeth at baseline showing status according to the (i) ElectricalConductance and (ii) Visual-Tactile methods utilized. Detection methodsElectrical Conductance Visual-Tactile First Molar Teeth (6) (number)(number) in Quadrants 1-4 Sound Carious Sound Carious 16 7 (5.9) 112(94.1)  81 (68.1) 38 (31.9) 26 21 (17.6) 98 (82.4) 80 (67.2) 39 (32.8)36 26 (21.8) 93 (78.2) 45 (37.8) 74 (62.2) 46 24 (20.2) 95 (79.8) 52(43.7) 67 (56.3) Total 78 (16.4) 398 (83.6) 258 (54.2) 218 (45.8)Carious/sound ratio 5.10 0.84 Values in parentheses are expressed inpercentages.

TABLE7 Number and percentage of occlusal surfaces in first permanentmolar teeth at 14 months showing status according to the (i) ElectricalConductance and (ii) Visual-Tactile methods utilized. Detection methodsElectrical Conductance Visual-Tactile First Molar Teeth (6) (number)(number) in Quadrants 1-4 Sound Carious Sound Carious 16 4 (3.4) 115(96.6) 68 (57.2) 51 (42.8) 26 4 (3.4) 115 (96.6) 63 (53.0  56 (47.0) 369 (7.6) 110 (92.4) 33 (27.7) 86 (72.3) 46 9 (7.6) 110 (92.4) 24 (20.2)95 (79.8) Total 26 (5.5)  450 (94.5) 188 (39.5)  288 (60.5) Carious/sound ratio 17.30 1.53 Values in parentheses are expressed inpercentages.

At baseline, the electrical conductance (EC) method detected many moreocclusal surfaces with caries lesions than was observed with thevisual-tactile procedure (see Table 6 and particularly the carious/soundratios shown therein; i.e. 5.10 by EC and 0.84 by visual-tactile). Thiswide difference can be attributed to the wide difference in theirdetection capabilities, namely that EC examination is capable ofdetecting lesions at a much earlier stage in their development than canbe detected by visual-tactile means, when many very early lesions arenot yet visible by visual-tactile examination. A second examination wasdone 14 months after baseline to enable lesions to develop and thusbecome more readily detectable by both methods. The results showed thatcaries increased between baseline and 14 months by both methods (Tables6 and 7 and see FIG. 11). From Tables 6 and 7, one can see that withtime (i.e. after 14 months) the higher ratio of carious to soundsurfaces is sustained as caries progresses with age (i.e. 17.30 by ECand 1.53 by visual-tactile). FIG. 11 clearly shows the much greatercaries detection capability with EC measurement than with the classicalmirror and probe method, which is what should be expected because of themuch greater and earlier detection capability by EC measured with thedevice of the present invention.

Earlier detection by electrical conductance is particularly valuable atthe pre-cavity stage of caries development, because there are majortreatment consequences of early detection. Most significant is thattreatment can be achieved by simpler means, namely re-mineralizationprocedures, whereas later detection by visual-tactile means involveslarger lesions (cavities) and use of so-called drilling and fillingrestorative procedures.

Example 6

The size and shape of the removable measuring tips of the device of thepresent invention are important features. The probe tips are able to fitinto caries-prone sites more readily than heretofore. Probe tips rangingin tip sizes were tested and compared to the probing ends of a range ofexplorer probes normally used in conjunction with hand mirrors to probefor and locate presence of early cavities.

Probing tips ranging from 0.12 to 0.73 mm in diameter at their actualtips were examined for their ability to measure electrical conductancein molar teeth using the apparatus described in Example 1. Results arepresented in FIG. 8. Tips with a diameter ranging from 0.12 to 0.40 mmgave similar results. For tips with diameters greater than 0.40 mm,electrical conductance values, measured in μA, dropped as would beexpected because the tip would not be able to penetrate and fitsufficiently into a pit, fissure or fossa site.

Similar electrical conductance measurements were also made for a rangeof commercially available dental explorers coupled to the device ofExample 1 (FIGS. 9 and 10). Their tip diameters were larger in size thanthe described tip diameters proposed herein and hence caries-prone sitepenetration can be expected to be less, as in FIG. 9 and even less as inFIG. 10 These explorers are available commercially and comprise arepresentative sample. Their tips are larger and slightly more roundedat their tips than are the tips of the present invention. Accordingly,the tips of the present invention were more suitably shaped and finerthan the commercial explorer tips and thus could penetrate into occlusalsites more readily. The results in FIG. 10 showed virtually noelectrical conductance which is consistent with penetration of theprobes being insufficient to give much current flow. FIG. 9 indicatessome penetration. Thus, the size of the prior art tips limited theirability to penetrate sufficiently into caries prone sites and hencemeant unsatisfactory and less sensitive diagnostic capability. Thislimitation also applies to tufted tips (i.e. bundle of tufts) presentlyavailable. Such tufts cannot penetrate fissures deeply and theirbehaviour is like that of the oversized electrodes in FIGS. 8, 9 and 10.Also such a tufted electrode tip lacks the rigidity that enablesreproducable probe placement into a fissure site.

What is claimed is:
 1. A device for detecting non-cavitated caries lesions, comprising: a measuring electrode having an electrically conductive tip, said tip being dimensionally configured to fit within a fissure and provide electrical contact with a patient's tooth; a reference electrode, the reference electrode being configured for electrical contact with the patient's body; and measuring means for determining electrical conductance between the measuring electrode and the reference electrode, wherein the device is further configured to receive a current source for providing electrical current between the measuring electrode and the reference electrode. 